JP2018019163A - Image reading device - Google Patents

Abstract

An image reading apparatus capable of suppressing the influence of regular reflection on a document while suppressing an increase in size of the apparatus. A document illuminated by a first illumination light that alternately repeats a bright state and a dark state, and a second illumination light that becomes bright when the first illumination light is in a dark state. An imaging optical system that forms an image; an imaging element that receives light from the imaging optical system to acquire image information; and first image information acquired when the first illumination light is in a bright state; A first determination unit that determines whether or not the first illumination light is regularly reflected on the document based on the second image information acquired when the first illumination light is in a dark state; A generation unit configured to generate an image of the document based on the first and second image information when the first determination unit determines that the regular reflection is present. [Selection] Figure 2

Description

  The present invention relates to an image reading apparatus, and is particularly suitable for an image reading apparatus that collectively reads an area by an overhead reading method.

  2. Description of the Related Art Conventionally, as an image reading apparatus that reads image information from above, an image reading apparatus that captures an image of a document surface placed on a document table from above by an image sensor and acquires image information on the document surface is known.

  Here, when the original is made of glossy paper or flat plastic, the image information may be acquired in a state where the illumination light is regularly reflected on the surface of the original depending on the arrangement state of the light source that illuminates the original. In this case, the image information of the portion where specular reflection has occurred becomes a so-called “saturation” image in which the luminance is high and saturated, or the image information cannot be read because the image information has high luminance. This causes problems such as unevenness in density.

  For this reason, an image reading apparatus has been proposed in which the influence of such regular reflection light is reduced and avoided. Japanese Patent Application Laid-Open No. 2004-133867 provides position changing means for changing the shooting position of a subject so that a plurality of different subject images are formed on the image sensor, and a plurality of shot image data is synthesized. An image reading apparatus for obtaining image data having no regular reflection portion is disclosed.

  Further, Patent Document 2 discloses a first polarization unit that covers a portion other than an opening where a subject can be placed and removed, and transmits a component in one direction of light emitted to the placement unit, and first polarized regular reflection light. An image reading apparatus including a second polarization unit that transmits only a component in a direction intersecting the direction of the component is disclosed.

JP-A-8-307657 JP 2009-141511 A

  However, in the prior art disclosed in Patent Document 1, when the light source of specular reflection light is long like a fluorescent lamp, the direction changed by the position changing means is along the long direction of the fluorescent lamp. Even if the position is changed, the specularly reflected light remains in the same place. In order to cope with the direction other than the long direction of the fluorescent lamp by the position changing means, it is necessary to change the position two-dimensionally, which increases the size of the apparatus.

  Moreover, in the prior art disclosed in Patent Document 2, since the entire periphery of the subject other than a part of the opening is covered, when the subject becomes large, the device that covers it becomes large. Further, since a part of the illumination light is cut by the polarization means, it is necessary to increase the light quantity of the light source in order to obtain a necessary illumination light quantity. This raises the temperature of the light source and the polarization means, and the cooling means is also necessary. The device becomes larger.

  An object of the present invention is to provide an image reading apparatus capable of suppressing the influence of regular reflection on a document while suppressing the enlargement of the apparatus.

  In order to achieve the above object, an image reading apparatus according to the present invention includes a first illumination light that alternately repeats a bright state and a blinking state, and a first illumination light that enters a bright state when the first illumination light is in a blinking state. An imaging optical system that forms an image of a document illuminated by the illumination light, an imaging element that receives light from the imaging optical system and obtains image information, and the first illumination light is in a bright state Specular reflection of the first illumination light on the document based on the first image information acquired at the time and the second image information acquired when the first illumination light is in the dark state An image of the original based on the first and second image information when the first determination unit determines that there is the regular reflection by the first determination unit. And a generation unit.

  According to the present invention, it is possible to provide an image reading apparatus capable of suppressing the influence of regular reflection on a document while suppressing the enlargement of the apparatus.

1 is a schematic perspective view of an image reading apparatus according to an embodiment of the present invention. 1 is a schematic sectional view of an image reading apparatus according to an embodiment of the present invention. 6 is a flowchart in the regular reflection light avoidance mode of the image reading apparatus according to the first embodiment. The figure which shows the flicker state of the fluorescent lamp which concerns on 1st Embodiment The figure which shows the sensor output obtained by the regular reflection area | region detection operation | movement which concerns on 1st Embodiment. The figure which showed the relationship between the flicker which concerns on 1st Embodiment, and two imaging | photography timings The figure which showed typically the image composition which concerns on 1st Embodiment Schematic sectional view of an image reading apparatus according to the second embodiment Flowchart in the regular reflection avoidance mode of the image reading apparatus according to the second embodiment

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image reading device)
FIG. 1 is a schematic perspective view of an image reading apparatus according to an embodiment of the present invention. 101 is an image reading apparatus main body (apparatus main body), 102 is a document table, 103 is a frame indicating a document placement position, and 104 is a document. At the time of image reading, the original 104 arranged upward in the frame 103 is picked up by an image pickup device incorporated in the apparatus main body 101, and the original image is output to a storage device, a printer, or a monitor (not shown).

  The document table 102 does not need to be integrated with the apparatus main body 101. If there is a flat part such as a desk or a table, the same function can be exhibited by placing the apparatus main body 101 thereon. It should be noted that the frame 103 indicating the document placement position may be a mat such as a mat that indicates where the document 104 is placed.

  FIG. 2 is a schematic cross-sectional view of the image reading apparatus according to the present embodiment. Reference numeral 105 denotes a power source, 106 denotes an imaging device, and 107 denotes a circuit board. The image pickup apparatus 106 includes an image pickup optical system and an image pickup element (two-dimensional image pickup element) that is provided on the image plane of the image pickup optical system and receives light from the image pickup optical system to acquire image information, and is driven by a power source 105. It is controlled by a chip mounted on the circuit board 107. In the present embodiment, the imaging device 106 is provided in an upper space in the vertical direction with respect to the document so that image information of the document can be read from above. At this time, the image sensor is provided at a position closer to the document than the document table on which the document is placed.

  In FIG. 2, reference numeral 108 denotes a fluorescent lamp, which also represents first illumination light (illumination light 1) that repeats a bright state and a dark state alternately. Reference numeral 109 denotes external light (for example, sunlight) as second illumination light (illumination light 2) that illuminates the document when at least the first illumination light is in the dark state.

  It should be noted that the regular reflection of the document due to the illumination light of the fluorescent lamp 108, which will be described later, must be taken into consideration, while the external light 109 has an incident angle with respect to the normal of the document surface larger than the illumination light from the fluorescent lamp 108. The light amount of the external light 109 is generally smaller than the light amount of the fluorescent lamp 108, and it is not necessary to consider the regular reflection of the document by the external light.

  Here, the bright state in this specification refers to an illumination state in which the light amount in the first illumination light is 80% to 100% of the peak light amount. The extinction state refers to an illumination state in which the light amount in the first illumination light is 0% to 20% of the peak light amount.

  A more preferable bright state refers to an illumination state in which the light amount in the first illumination light is 90% to 100% of the peak light amount. A more preferable extinction state refers to an illumination state in which the light amount in the first illumination light is 0% to 10% of the peak light amount.

  In the present embodiment, the fluorescent lamp 108 that repeatedly blinks at 50 Hz or 60 Hz according to the driving frequency is attached to the ceiling and illuminates the entire area of the original 104 including the original 104. Since the apparatus main body 101 is generally installed indoors, the external light 109 incident from a window or the like also illuminates the document 104.

  Here, if the original 104 has a large light diffusivity such as normal recording paper (copy paper), the problem that the image information cannot be read does not occur because specular reflection light is hardly generated. However, when the original 104 is glossy such as a license or photographic paper, a part of the light of the fluorescent lamp 108 above the vicinity of the apparatus body 101 (dotted line in FIG. 2) is regularly reflected on the surface of the original 104. Wake up.

  That is, the image pickup device 106 cannot read the document image information at the portion where the light from the fluorescent lamp 108 has been specularly reflected (the portion where the arrow dotted line in FIG. 2 is bent), and the fluorescent lamp 108 is captured as an image.

  Here, the external light 109 is incident from a window or the like. However, since the incident angle is larger than that of the fluorescent lamp 108 on the ceiling, the specularly reflected light of the external light 109 (the one-dot chain line in FIG. 2) is below the imaging device 106. Head to the side. That is, other than the regular reflection light of the external light 109 is incident on the imaging device 106, and the regular reflection light of the external light 109 is not incident.

  In the present embodiment, as described below, the problem of imaging the regular reflection light of the fluorescent lamp 108 using the external light 109 is solved. In the present embodiment, a first determination unit (CPU 110 in FIG. 2) that determines the presence or absence of regular reflection on the document by the illumination light of the fluorescent lamp 108, and the bright state and the dark state are alternately repeated as the document illumination light. It has the 2nd determination part (CPU110 of FIG. 2) which determines the presence or absence of a component.

(flowchart)
FIG. 3 is a flowchart when the image reading apparatus according to this embodiment is in the regular reflection avoidance mode. The avoidance of missing image information due to the regular reflected light of the fluorescent lamp 108 will be described with reference to this flowchart.

  First, the regular reflection avoidance mode is selected from the apparatus main body 101 or a PC (personal computer, personal computer) (not shown) connected to the image reading apparatus, and the regular reflection avoidance mode is started (S101).

1) Flicker detection (preliminary operation before shooting)
Next, a flicker detection operation is performed in the above-described second determination unit (CPU 110 in FIG. 2) (S102). Since the fluorescent lamp 108 is driven by an AC power supply, the amount of light of the original illumination repeatedly blinks according to the frequency (so-called flicker exists). FIG. 4 shows the temporal change in the amount of illumination light obtained by adding the illumination light (illumination light 1) from the fluorescent lamp and the illumination light (illumination light 2) from the external light corresponding to the temporal change in output at a predetermined pixel of the image sensor. Show.

  That is, in the flicker detection operation (S102), the imaging device 106 is driven to continuously output the brightness of the document surface, and output information as shown in FIG. 4 is obtained. Since the fluorescent lamp 108 is driven by an AC power source, blinking is repeated as shown in FIG. 4 according to the frequency. For example, blinking is repeated at a frequency such as 50 Hz, but it does not disappear or turn on instantaneously but gradually changes as shown in the figure. Such blinking is stored in the storage means mounted on the circuit board 107 for the number of times within a predetermined time.

  Next, flicker detection (S103) is performed. From the information obtained in the flicker detection operation (S102), the periodicity of the change in the amount of light is obtained. For example, when blinking 10 times within a predetermined time, the change in the light quantity is measured 10 times, and each light quantity change time (T1, T2, T3, .., T10) falls within 10%, it is determined that there is periodicity and flicker. On the other hand, if the condition is not met, it is determined that there is no periodicity and flicker is not caused.

  When the flicker is determined, an arbitrary peak light amount and bottom light amount, or an average of 10 peak light amounts and an average of bottom light amounts are acquired. Further, the information of the average time A and the half time A / 2 shown in FIG. 4 is stored in the storage means mounted on the circuit board 107, and the process proceeds to the regular reflection area detection operation based on the determination of Yes (S104). On the other hand, if it is determined that there is no flicker, the process proceeds to END in the regular reflection avoidance mode based on the determination of No (S110).

  In the case of proceeding to the regular reflection area detection operation (S104), FIG. 5 shows a part of information obtained by the regular reflection area detection operation (S104). 5A, 5 </ b> B, 5 </ b> C, and 5 </ b> D are outputs of one line when the original 104 is read by the imaging device 106, the horizontal axis is the pixel position, and the vertical axis is the luminance output. . Note that although one line is used for the sake of explanation, the concept is the same for a plurality of lines.

  In FIG. 5, (a) and (b) show the output in the case of fluorescent lamp + external light, and (c) and (d) show only the external light. An alternate long and short dash line parallel to the horizontal axis is a threshold value for determining that the output value is regular reflection. This threshold value may be set to a value at which the luminance is saturated, or may be set to a value slightly smaller than that.

2) Regular reflection detection (preliminary operation before shooting)
Next, regular reflection detection is performed in the first determination unit (CPU 110 in FIG. 2) described above (S105). If the output obtained in the regular reflection detection operation (S104) is larger than the threshold value as shown in FIG. 5B, the specular reflection light may be read. If the output is smaller than the threshold value as shown in FIG. Indicates that regular reflection light is not read. If the output is equal to or lower than the threshold as shown in FIG. 5A, it is determined that the regular reflection light is not read, and the process proceeds to END in the regular reflection avoidance mode based on the determination of No (S110).

  Here, even if it is larger than the threshold value as shown in FIG. For example, when the original 104 has a silver color with a high reflectance, the output becomes large even when the regular reflection light is not read. For this reason, a comparison is made with the output when the fluorescent lamp is extinguished, that is, when there is only external light.

  That is, if the output profile is only for external light as shown in FIG. 5D and the profile is similar to (similar to) the output profile shown in FIG. It is determined that the regular reflection light is not read. Then, based on the determination of No, the process proceeds to END in the regular reflection avoidance mode (S110). On the other hand, if the output profile of only external light as shown in FIG. 5C is not close to (or similar to) the output profile of FIG. 5B, it is determined as regular reflection, and the process proceeds to exposure amount & exposure timing calculation. (S106).

3) Determination of shooting conditions for two shots (preliminary operation before shooting)
Next, a photographing exposure amount and photographing timing (imaging timing, exposure timing) are calculated as photographing conditions for photographing the original 104 (image reading) (S106). Specifically, the photographing exposure amount and photographing timing are calculated from the light amount and period data stored in the storage means in flicker detection (S103). Here, shooting (image reading) is performed twice (shooting in the bright state and shooting in the dark state when the illumination light has a component that alternately repeats the bright state and the dark state). calculate.

  FIG. 6 is a diagram showing the relationship between flicker and two shooting timings (imaging timings). FIGS. 6A, 6B, and 6C show changes in the amount of light when the illumination light 1 of the fluorescent lamp 108, the illumination light 2 that is the external light 109, and the illumination light 1 and the illumination light 2 are illuminated simultaneously, respectively. Where the horizontal axis represents time and the vertical axis represents the amount of light.

  As shown in FIG. 6A, in the illumination light 1, as described above, flicker whose light amount fluctuates at a constant period is generated. As shown in FIG. 6B, since the illumination light 2 is external light (for example, sunlight incident from a window), there is almost no change in the change of the time for photographing the document. Even if it is clouded and fluctuates, no periodic change occurs. And as shown in FIG.6 (c), what combined these illumination light 1 and illumination light 2 becomes an actual light quantity change.

  Of the two shootings (image reading) for acquiring the first and second image information, the first shooting for acquiring the first image information is a state in which regular reflection occurs, that is, the peak of the light amount change. (Timing timing, exposure timing). The photographing exposure amount is the exposure time at least when the first and second image information is obtained so as to reduce the relative brightness change at the position corresponding to the first and second image information. (Shutter) and / or aperture diameter is adjusted. At this time, the sensor sensitivity is adjusted in the same manner as in normal shooting.

  The second shooting for acquiring the second image information is performed in a state in which only regular light is not generated, that is, a timing (shooting timing) that becomes the bottom of a change in the amount of light. Specifically, an interval from the first shooting to the second shooting is called as a half cycle time A / 2 based on one cycle of data A stored in the storage means. Note that, here, a half-cycle time A / 2 is taken as an example, but the same effect can be obtained even when A / 2 + A × n (n is an integer).

  The shooting exposure amount for the second shooting is determined so that a region that cannot be read due to regular reflection can be read. That is, the photographing exposure amount at this time is determined so that the region where the specular reflection occurs stored in the storage means in the specular reflection detection (S105) can be read. As much as possible, it is preferable to set so that noise is reduced during image composition (S109).

Next, it changes so that it may become the exposure amount & exposure timing computed as mentioned above (S107). That is, based on the shooting conditions calculated in the exposure amount & exposure timing calculation (S106), the exposure amount is changed by changing the aperture and shutter speed of the imaging optical system from the already set shooting conditions, The time from the first shooting to the second shooting is changed.
As for the second shooting, as shown in FIG. 6C, the first time is near the peak of the flicker light amount change cycle, and the second time is the bottom when the light amount after 1/2 of the flicker light amount change cycle is small from the first time. It is in the vicinity.

4) Two times of photographing Next, photographing is performed based on the photographing condition changed in the exposure amount & exposure timing change (S107) (S108). At this time, while performing the flicker detection operation again for the first shooting, the first shooting is performed at the timing near the peak of the light amount change, and the image 1 is obtained. Then, the second shooting is performed at the set second exposure timing, and an image 2 is obtained. Then, the image data of the two images (image 1 and image 2) are stored in the storage means mounted on the circuit board 107.

5) Image Composition Next, the CPU 110 (FIG. 2) as the composition unit performs composition (image composition) on the original image with reduced regular reflection (S109). The synthesizing unit in the present embodiment synthesizes the image of the document by replacing the image information of the regular reflection area where the output is saturated in the first image information with the image information of the corresponding area in the second image information. That is, the synthesis unit can be said to be a generation unit that generates an image of a document in which regular reflection is suppressed when regular reflection is present.

  FIG. 7 schematically shows image composition. There are an image 1 obtained by the first photographing and an image 2 obtained by the second photographing, and the white portion of the image 1 is a place where information is lost due to specular reflection light. The dotted line in image 2 is the same as the white spot in image 1 and the fluorescent lamp 108 that has become the specularly reflected light is turned off and shot with external light 109. Information remains. Therefore, if the white portion of the image 1 is brought from the image 2 and synthesized, and the difference in brightness is corrected, an image with no missing image information like the image 3 can be obtained.

  In this way, the regular reflection light avoidance mode becomes END (S110). If the result of flicker detection (S103) or regular reflection detection (S105) is No, it is determined that the regular reflection avoidance mode is unnecessary, and the regular reflection avoidance mode is END (S110). For example, there is a case where the regular reflection avoiding mode has been set although no regular reflection has occurred.

  As described above, according to the present embodiment, it is possible to avoid the enlargement of the apparatus and to suppress the influence of regular reflection on the original. That is, it is possible to avoid the case where the image information cannot be read due to the regular reflection light or the case where the density is uneven.

<< Second Embodiment >>
FIG. 8 is a schematic sectional view of an image reading apparatus according to the second embodiment of the present invention. 801 is an image reading apparatus main body (apparatus main body), 802 is a document table, 803 is a sheet indicating a document placement position, 804 is a document, 805 is a power source, 806 is an imaging device, 807 is a circuit board, 808 is a fluorescent lamp, 809 Is an LED lighting device. The imaging device 806 includes an imaging optical system and an imaging element, and is controlled by a chip mounted on a circuit board 807 driven by a power source 805.

  In FIG. 8, reference numeral 808 denotes a fluorescent lamp, which also represents the first illumination light (illumination light 1). Reference numeral 809 denotes an LED illumination device, which also represents second illumination light (illumination light 2). A fluorescent lamp 808 that repeatedly flickers at 240 Hz according to the driving frequency is attached to the ceiling and illuminates the entire area of the original 804 including the original 804. Further, the document 804 is also illuminated from the LED illumination device 809 built in the apparatus main body 801. The LED illumination device 809 including a light source that emits the second illumination light (illumination light 2) is controlled by a chip mounted on the circuit board 807 so as to be continuously lit.

  As in the first embodiment, part of the light beam emitted from the fluorescent lamp 808 travels as indicated by the dotted line and generates specularly reflected light. At this time, the light emitted from the LED illumination device 809 proceeds as indicated by a one-dot chain line arrow, and the specularly reflected light does not enter the imaging device 806, so that there is no problem that the imaging device 806 images the regular reflection light.

  In the present embodiment, a first determination unit (CPU 810 in FIG. 8) that determines whether or not regular reflection is performed on the document by illumination light from the fluorescent lamp 108, and a bright state and a dark state are alternately repeated as document illumination light. It has the 2nd determination part (CPU810 of FIG. 8) which determines the presence or absence of a component.

(flowchart)
FIG. 9 is a flowchart when the image reading apparatus according to this embodiment is in the regular reflection avoidance mode. The avoidance of missing image information due to regular reflection light will be described with reference to this flowchart. The basic flow is the same as in the first embodiment. LED lighting device lighting (S202) is added after START (S201), and LED lighting device extinguishing (S211) is added after image composition (S210).

  The present embodiment is a case where the apparatus main body is installed in a room such as a conference room having no window or the like, and the apparatus main body even when the outside light does not reach the first embodiment using the outside light. By using the LED illumination device 809 built in 801, the influence of regular reflection can be suppressed.

  As described above, this embodiment can also avoid an increase in the size of the apparatus and suppress the influence of regular reflection on a document. That is, it is possible to avoid the case where the image information cannot be read due to the regular reflection light or the case where the density is uneven.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Modification 1)
In the above-described embodiment, at least one of the first illumination light that alternately repeats the bright state and the dark state and the second illumination light that illuminates the document when the first illumination light is in the dark state, at least one of the devices is an apparatus. Although it exists outside the main body, the present invention is not limited to this. In other words, both the light source that emits the first illumination light that alternately repeats the bright state and the dark state and the light source that emits the second illumination light may be incorporated in the apparatus main body.

(Modification 2)
In the above-described embodiment, the second illumination light is continuous light, but the second illumination light is different in phase from the first illumination light and may be illumination light that alternately repeats the bright state and the dark state. good.

DESCRIPTION OF SYMBOLS 101 ... Image reading apparatus main body, 102 ... Document base, 103 ... Frame which shows document mounting position, 104 ... Document, 105 ... Power supply, 106 ... Imaging device, 107 ... Circuit board 108... Illumination means 1 (fluorescent lamp) 109... Illumination means 2 (external light)

Claims (13)

Imaging that forms an image of a document illuminated by a first illumination light that alternately repeats a bright state and a dark state and a second illumination light that becomes bright when the first illumination light is dark Optical system,
An image sensor that receives light from the imaging optical system and acquires image information;
Based on the first image information acquired when the first illumination light is in a bright state and the second image information acquired when the first illumination light is in a dark state, the first A first determination unit for determining the presence or absence of regular reflection of the illumination light on the original;
A generation unit configured to generate an image of the document based on the first and second image information when the first determination unit determines that the regular reflection is present;
An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein the first determination unit determines the presence or absence of the regular reflection based on partial output information of the image sensor.   2. A second determination unit that determines whether or not a bright state and a dark state are alternately repeated based on a temporal change in output in the first pixel of the image sensor. 3. The image reading apparatus according to 2.   The said 2nd determination part determines the imaging timing which acquires the said 1st and 2nd image information based on the average of the period which repeats a bright state and a dark state alternately. Image reading device.   The exposure amount is adjusted at least when the first and second image information is obtained so as to reduce a relative brightness change at a position corresponding to each other in the first and second image information. The image reading apparatus according to claim 1, further comprising at least one of a shutter and a diaphragm.   The generating unit generates the image of the original by replacing the image information of the regular reflection area in which the output is saturated in the first image information with the image information of the corresponding area in the second image information. The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.   The image reading apparatus according to claim 1, wherein incident angles of the first illumination light and the second illumination light with respect to the document are different from each other.   The image reading apparatus according to claim 7, wherein an incident angle of the second illumination light with respect to the original is larger than an incident angle of the first illumination light with respect to the original.   The image reading apparatus according to claim 7, further comprising a light source that emits the second illumination light.   The image reading apparatus according to claim 1, wherein the second illumination light illuminates the original even when the first illumination light is in a bright state.   11. The second illumination light according to claim 1, wherein the second illumination light is an illumination light having a phase different from that of the first illumination light and alternately repeating a bright state and a dark state. Image reading apparatus.   The image reading apparatus according to claim 1, further comprising a fluorescent lamp as a light source that emits the first illumination light.   The image reading apparatus according to claim 1, wherein the image sensor is provided at a position closer to the document than a document table on which the document is placed.